A flat display, represented by a liquid crystal display, is thin in thickness, lightweight and low in power consumption, and hence has recently been used as a display for a variety of devices. In these days, to further reduce the thickness, weight and cost, such a technique has been established in which a driving circuit is constructed using low-temperature polysilicon thin-film transistors, higher in electron mobility than conventional amorphous silicon thin-film transistors, and in which the so constructed driving circuit is formulated as one with a glass substrate.
As a driving circuit, a CMOS (Complementary MOS) circuit, made up of an NMOS transistor and a PMOS transistor, is routinely used. However, this technique suffers a problem that the manufacturing process has many process steps and hence is costly. To solve this problem, such a driving circuit composed only of transistors of one polarity, that is, only one of a set of NMOS transistors or a set of PMOS transistors, has been proposed. In Patent Document 1, a shift register composed only of a set of PMOS transistors (FIG. 2 of Patent Document 1) is described. The shift register of Patent Document 1 is composed of PMOS transistors T1 to T8, and yields an output signal OUT by activating power supply VDD and entering input signal IN and clock signals C1 to C3.
Meanwhile, there is an increasing demand for higher resolution of a liquid crystal device. The reason is that, if the resolution is improved, the amount of the information that may be displayed at a time is increased, thus improving the added value of the liquid crystal display.
In general, each pixel of a display is made up of a sub-pixel for representing red, a sub-pixel for representing green and a sub-pixel for representing blue. The respective sub-pixels are arranged in a transverse direction on a display surface. This pixel array is also termed a vertical stripe system. There is also proposed a pixel array, termed a transverse stripe system, in which the sub-pixels are arranged along the vertical direction of the display surface. In Patent Document 2, a pixel array of the transverse stripe system (FIG. 2 of Patent Document 2) is described. Referring to FIG. 2 of Patent Document 2, pixel 110 is composed of vertically arranged sub-pixels 120 of R, G and B. Scanning circuit 350, driving a plurality of scanning lines 311 for the respective sub-pixels 120, includes outputs Y1-R, Y1-G, Y1-B to Y320-R, Y320-G and Y320-B. Since the number of effective pixels of liquid crystal panel 100 in the transverse direction is 240 and that in the vertical direction is 320, scanning circuit 350 has a number of outputs equal to thrice the number 320 of the effective pixels in the vertical direction.
In Patent Document 3, another technique regarding the pixel array of the transverse stripe system (see FIGS. 2 and 3 of Patent Document 3) is described. Referring to FIGS. 2 and 3 of Patent Document 3, display pixel 10 is divided in the horizontal direction into a sub-pixel for a left eye and a sub-pixel for a right eye. In addition, the sub-pixel for the left eye and the sub-pixel for the right eye are each divided in the vertical direction into sub-pixels for R, G and B. That is, each pixel is divided into six sub-pixels. Gate line driving circuit 8, driving display pixel 10, includes outputs Y(1) to Y(1440). That is, gate line driving circuit 8 includes a number of outputs equal to three times the number 480 of pixels in the vertical direction.
The technique described in Patent Document 4 is directed to a scanning line driving circuit capable of partial representation. The technique disclosed implements the partial display function with the use of a smaller number of elements (FIG. 4 of Patent Document 4).    [Patent Document 1] JP Patent Kokai Publication No. JP-P2002-313093A (FIG. 2)    [Patent Document 2] JP Patent Kokai Publication No. JP-P2006-317566A (FIG. 2)    [Patent Document 3] JP Patent Kokai Publication No. JP-P2006-030512A (FIGS. 2 and 3)    [Patent Document 4] JP Patent Kokai Publication No. JP-P2008-140490A (FIG. 4)